The present invention relates to a storage system, more specifically, dynamic load balancing in a storage system having a plurality of host interfaces and processors.
Data is the underlying resources on which all computing processes are based. With the recent explosive growth of the Internet and e-business, the demand on data storage systems has increased tremendously. Generally, storage networking encompasses two applications or configurations: network-attached storage (NAS) or storage area network (SAN). A NAS uses IP over Ethernet to transports data in file formats between storage servers and their clients. In NAS, an integrated storage system, such as a disk array or tape device, connects directly to a messaging network through a local area network (LAN) interface, such as Ethernet, using messaging communications protocols like TCP/IP. The storage system functions as a server in a client-server system.
Generally, a SAN is a dedicated high performance network to move data between heterogeneous servers and storage resources. Unlike NAS, a separate dedicated network is provided to avoid any traffic conflicts between client and servers on the traditional messaging network. A SAN permits establishment of direct connections between storage resources and processors or servers. A SAN can be shared between servers or dedicated to a particular server. It can be concentrated in a single locality or extended over geographical distances. SAN interfaces can be various different protocols, such as Fibre Channel (FC), Enterprise Systems Connection (ESCON), Small Computer Systems Interface (SCSI), Serial Storage Architecture (SSA), High Performance Parallel Interface (HIPPI), or other protocols as they emerge in the future. For example, the Internet Engineering Task Force (IETF) is developing a new protocol or standard iSCSI that would enable block storage over TCP/IP, while some companies are working to offload the iSCSI-TCP/IP protocol stack from the host processor to make iSCSI a dominant standard for SANs.
Regardless of the types of storage system used, storage systems are increasingly required to store larger capacity and provide higher performance. To satisfy these requirements, the storage controllers for the enterprise or midrange storage systems have been provided with a plurality of processors. For example, Hitachi Lightning 9900™ comprises a plurality of Client-Host Interface Processors (CHIPs) to process multiple concurrent input and output request (“I/Os”).
One issue of a NAS system is that the load balancing among multiple processors may be difficult. Sharing a volume or file system among multiple NAS processors (the processors that processes NFS/CIFS requests) may be difficult since a NAS processor caches the accessed data in their memory. This tends to make it difficult to maintain coherency or consistency for the cached data since there are multiple processors. Therefore, a file access request is generally processed one NAS processor at a time, not fully utilizing the multiple processors. Accordingly, among other features, it would be desirable to provide a good load balancing among multiple processors.